Method? How do you mean. You're going to have be more specific.
Each airdrop has it's own unique requirements. Some of them you simply have to hold some coins, in order to get more. For others, you have to jump through a shitload of hoops and dance around like a marketing monkey doing all the heavy lifting for the project. All depends on what the requirements are.
I spent a three month period to see if airdrops were worth it. And I can say, 99.9% of them are not. You may find a diamond in the rough but those are increasingly difficult to find. I gave up after 3 months because my time is better spent doing things which have a much higher ROI like day trading.
Work smarter, not harder.